Electric heater element



Nov. 10, 1959 T. s. KINNEY 2,912,654

ELECTRIC HEATER ELEMENT Filed Nov. 9, 1956 INVENTOR. 4 THEODO E s.KINNEY ELECTRIC HEATER ELEMENT Theodore S. Kinney, Bellevue, Wash.

Application November 9, 1956, Serial No. 621,260

El Claim. (Cl. 338-229) This invention relates to improvements in anelectric heater element for liquid tanks, and more particularly, relatesto a heater element of high wattage, compact design for installation ina tubular heater housing.

Among the more-important objects of this invention are the provision ofan electric heater element which has a maximum of heat generatingability in a minimum of mass, which is adaptable to and may be installedin existing tubular housing without requiring alteration of such housingand without the likelihood of damage to such housing, and which issimple to construct and easy of installation.

These and other objects of this invention will be apparent during thecourse of the following description. I set forth herein a preferredembodiment of my invention. Such changes and modifications as will occurto those skilled in this art and which are the fair equivalents of thisinvention are contemplated a part of this invention and to be covered bythe subjoined claim.

In the drawings:

Figure 1 is a fragmentary elevation view of a fluid tank containing myheater element;

Figure 2 is an enlarged cross-section view taken on line 22 of Figure 1;

Figure 3 is an enlarged elevation view of my heater element withportions broken away and shown in section;

Figure4 is a schematic diagram of the coiled-wire element of my heater;

Figure 5 is a face view of an insulator body of my heater; and

Figure 6 is a face view of a junction block used in my heater.

Referring to Figure 1, within tank 10 is installed the tubular heaterhousing 12 having its inner end closed by cap 14 and its outer endsecured in the threaded and flanged bushing 16. Tank 10 has a threadedfitting 18 attached thereto into which bushing 16 is threadedly engaged.Tank 10 is typified by any conventional hotwater heater tank. Thetubular housing 12 is typical of many hundreds of thousands that havebeen installed over the years. Cap 14 is normally brazed into the end oftube 12. Tube 12 is normally hard soldered into bushing 16. It isimperative, when a low-wattage element as normally supplied with housing14 is replaced by a high wattage element, that these brazed and solderedwater-tight joints not be subjected to heat concentrations operable todestroy the bonds. It has been an object of this invention to provide aheater element which meets this requirement.

The heater element, designated as a whole in Figure 1 by the numeral 20,is cylindrical and closely fits within housing 12 being insertedlongitudinally through bushing 16.

As may be seen in Figure 3, the element comprises the inner spacer body22, the intermediate radiator bodies 24, and outer terminal body 26.Bodies 22, 24 and 26 are formed of high temperature ceramic materialsand have identical cross-sections most clearly illustrated in Figure 5.Each body is cylindrical and has a plurality of United States Patent 0grooves 30 symmetrically arranged in a radial manner relative thelongitudinal axis of the body. Each groove 30 has a restricted mouth 32formed by the closing together of the outer portions of the materialforming the walls of the grooves 30. On opposite sides of the body axisis a pair of smaller passages 34, 34. It will be noted that there is aneven number of grooves 30 in this preferred form of body. To aid incomprehension of this structure I prefer that such ceramic body beapproximately one and eleven-thirty-seconds inches in diameter and thatthe width of grooves 30 be one-quarter inch with a mouth ofapproximately one-eighth inch. The length of bodies 22, 24 and 26 variesfrom one-half inch for body 22, to about two inches with bodies 24, andbody 26 is about one and one-half inches long. These dimensions aretypical in a water heater in which the overall length of element 20would be about sixteen inches. Naturally these dimensions would bevaried for heaters of greater or lesser capacity yet without departingfrom the inventive principles involved here. For example, greaterdiameters and greater lengths may be employed and the heaters may beused in oil tanks and the like.

In Figure 4 I schematically show in plan the arrange ment of the coiledwire resistance element which is threaded into blocks 24 and 26 shown inelevation in Figure 3. From connector lug 36 terminal lead 38 isstraight for a distance slightly less than the length of body 26 and isthen coiled in sinuous runs 40 as is conventional with electricresistance elements. Runs 40 are physically par: allel to each otherand, by means of bends 42 are shown here in series arrangementelectrically. The other terminal lead 44 ends at lug 46. It will beapparent that an electrically parallel arrangement is also operable inthis apparatus. Deleterious effects on the element wires of juxtaposedelements are avoided by interposing, throughout the full length of theheater, a ceramic wall between each pair of element runs 40. Thisceramic wall is constituted by the ceramic material between any pair ofgrooves 30.

As shown in Figure 3 leads 38 and 44 are passed into the arms of lugs 36and 46 respectively and are then reversed and the free ends are twistedabout the standing part as at 48.

The terminal block 50 formed of similar ceramic material is essentiallyT-shaped in cross-section and comprises leg 52 and cross arms 54, 54. Itsupports a pair of bolts 56, 58 outstanding one on each side of leg 52from the underside of an arm 54. Each arm 54 is also posted to form apassage 60 through which the terminal leads 38 or 44 are passed.

In the assembly of Figure 3, a run 40 of the coiledwire resistanceelement passes through aligned grooves 30 of a series of bodies 24. Ateach end of an adjacent pair of runs a bend 42 straddles the wallmaterial separating adjacent grooves. This may be seen in Figure 3. Theresistance is sinuously arranged in the grooves 30 in the arrangementdepicted in Figure 4. Leads 38, 44 outstanding from the outer end of theseries of bodies 24 are passed into and through mating grooves 30 inbody 26, thence through one of the passages 60 whereupon the lug 36 or46 is attached and same secured to a bolt 56 or 58 I by a nut 62.

By arranging that all the holes 34 of bodies 22, 24 and 26 are alignedwith a similarly spaced pair of holes 64, 64 through block 50, a wirebent U-shaped to provide strands 66, 66 may be inserted from the outerend inward. The inner ends of wires 66, 66 pass through the spacer body22 and twist 68 secures them together and retains the bodies and elementin assembled relation.

This electric heater element may be installed in the tubular housing 12by longitudinal insertion. The terminal block 50 bears on and abuts theouter face of bushing 16. Supply conductor wires 70, 70 are thenconnected to bolts 56 and 58 and the heater will operate.

By means of the construction described and shown, when the heater isactivated and the coils 40 are radiant the heat generated passes outwardof grooves 30 through throats 32 and directly to the inner surface oftube 12 to heat the same. By this means I insure that the maximum amountof heat from the element to the heat/transfer surface be by directradiation and not only by conduction through the ceramic bodies. Thisarrangement eliminates any possibility of a serious accumulation of heatwithin the ceramic bodies, especially along their axis, which would tendto destroy them. Since no elementruns are located within the symmetricarrangement here there is likewise avoided any possible damage to theelement from over-heating. U a

The use of spacer body 22 separates the brazed in place cap 14 from theheat sufliciently to. avoid heat-destruction of the brazing. Likewiseterminal body 26 spaces the radiant heater element away from thesoldered junction between tube 12 and bushing 16'to avoid its injury ordestruction.

It will be seen from the foregoing that this apparatus effectivelyaccomplishes the stated and other apparent objectives with simplicityand certainty.

Having thus described my invention, I claim: An electric heater elementfor installation in a tubular ,metallic heater housing, comprising: aninner spacer body, an intermediate radiator body, and an outer terholesaligned; said intermediate radiator body being cylindrical and having aplurality of grooves radially disposed longitudinally along its outersurface, each said groove being inwardly enlarged relative the mouth ofthe groove for the reception of a coiled resistance element larger incross-section than said groove mouth; a coiled wire resistance element,sinuously laced into said grooves in continuous manner from a firstterminal end to a second terminal end, said terminal ends both beinglocated at the outer end of said radiator body, and said terminal bodyhaving'a pair of passages each to receive a terminal end for externalconnection to a power source and a U-shaped,

straight strand, wire loop inserted into said aligned holes from theouter end inward andhaving the inner strand ends joined together tosecure said bodies against endwise movement relative each other andproviding an extension protruding longitudinally from said spacer bodyto abut the inner face of the tubular housing and separate the innerspacer body therefrom.

References Cited in the file of this patent UNITED STATES PATENTS1,320,890' Moffat Nov. 4, 1919 1,394,518 Abbott Oct. 25,1921 7 1,715,287Head May 28, 1929 2,666,838 Krah et a1. Jan. 19, 1954 FOREIGN PATENTS105,946 Great Britain Apr. 30, 1917 5,323 Australia Dec. 24. 1926

